125 research outputs found
Effective-field-theory predictions of the muon-deuteron capture rate
We quantify the theoretical uncertainties of chiral effective-field-theory
predictions of the muon-deuteron capture rate. Theoretical error estimates of
this low-energy process is important for a reliable interpretation of
forthcoming experimental results by the MuSun collaboration. Specifically, we
estimate the three dominant sources of uncertainties that impact theoretical
calculations of this rate: those resulting from uncertainties in the pool of
fit data used to constrain the coupling constants in the nuclear interaction,
those due to the truncation of the effective field theory, and those due to
uncertainties in the axial radius of the nucleon. For the capture rate into the
channel, we find an uncertainty of approximately due to
the truncation in the effective field theory and an uncertainty of
due to the uncertainty in the axial radius of the nucleon, both of which are
similar in size to the targeted experimental precision.Comment: 4 pages, 2 figure
The deuteron-radius puzzle is alive: A new analysis of nuclear structure uncertainties
To shed light on the deuteron radius puzzle we analyze the theoretical
uncertainties of the nuclear structure corrections to the Lamb shift in muonic
deuterium. We find that the discrepancy between the calculated two-photon
exchange correction and the corresponding experimentally inferred value by Pohl
et al. [1] remain. The present result is consistent with our previous estimate,
although the discrepancy is reduced from 2.6 to 2 . The error
analysis includes statistic as well as systematic uncertainties stemming from
the use of nucleon-nucleon interactions derived from chiral effective field
theory at various orders. We therefore conclude that nuclear theory uncertainty
is more likely not the source of the discrepancy.Comment: updated according to referee's comment
Cavity-free vacuum-Rabi splitting in circuit quantum acoustodynamics
Artificial atoms coupled to surface acoustic waves (SAWs) have played a
crucial role in the recent development of circuit quantum acoustodynamics
(cQAD). In this paper, we have investigated the interaction of an artificial
atom and SAWs beyond the weak coupling regime, focusing on the role of the
interdigital transducer (IDT) that enables the coupling. We find a parameter
regime in which the IDT acts as a cavity for the atom, rather than an antenna.
In other words, the atom forms its own cavity. Similar to an atom coupled to an
explicit cavity, this regime is characterized by vacuum-Rabi splitting, as the
atom hybridizes with the phononic vacuum inside the IDT. This hybridization is
possible because of the interdigitated coupling, which has a large spatial
extension, and the slow propagation speed of SAWs. We work out a criterion for
entering this regime from a model based on standard circuit-quantization
techniques, taking only material parameters as inputs. Most notably, we find
this regime hard to avoid for an atom on top of a strong piezoelectric
material, such as LiNbO. The SAW-coupled atom on top of LiNbO can thus
be regarded as an atom-cavity-bath system. On weaker piezoelectric materials,
the number of IDT electrodes need to be large in order to reach this regime.Comment: 11 pages, 5 figure
Global sensitivity analysis of bulk properties of an atomic nucleus
We perform a global sensitivity analysis of the binding energy and the charge
radius of the nucleus O to identify the most influential low-energy
constants in the next-to-next-to-leading order chiral Hamiltonian with two- and
three-nucleon forces. For this purpose we develop a subspace-projected
coupled-cluster method using eigenvector continuation [Frame D. et al., Phys.
Rev. Lett. 121, 032501 (2018)]. With this method we compute the binding energy
and charge radius of O at more than one million different values of the
16 low-energy constants in one hour on a standard laptop. For relatively small
subspace projections, the root-mean-square error is about 1% compared to full
space coupled-cluster results. We find that 58(1)% of the variance in the
energy can be apportioned to a single contact-term in the -wave, whereas
the radius depends sensitively on several low-energy constants and their
higher-order correlations. The results identify the most important parameters
for describing nuclear saturation, and help prioritize efforts for uncertainty
reduction of theoretical predictions. The achieved acceleration opens up for an
array of computational statistics analyses of the underlying description of the
strong nuclear interaction in nuclei across the Segr\'e chart.Comment: 6 pages, 3 figures, Supplemental Material provided as ancillary
materia
Eigenvector Continuation and Projection-Based Emulators
Eigenvector continuation is a computational method for parametric eigenvalue
problems that uses subspace projection with a basis derived from eigenvector
snapshots from different parameter sets. It is part of a broader class of
subspace-projection techniques called reduced-basis methods. In this colloquium
article, we present the development, theory, and applications of eigenvector
continuation and projection-based emulators. We introduce the basic concepts,
discuss the underlying theory and convergence properties, and present recent
applications for quantum systems and future prospects.Comment: 20 pages, 17 figure
Targeting Acetylcholinesterase: Identification of Chemical Leads by High Throughput Screening, Structure Determination and Molecular Modeling
Acetylcholinesterase (AChE) is an essential enzyme that terminates cholinergic transmission by rapid hydrolysis of the neurotransmitter acetylcholine. Compounds inhibiting this enzyme can be used (inter alia) to treat cholinergic deficiencies (e.g. in Alzheimer's disease), but may also act as dangerous toxins (e.g. nerve agents such as sarin). Treatment of nerve agent poisoning involves use of antidotes, small molecules capable of reactivating AChE. We have screened a collection of organic molecules to assess their ability to inhibit the enzymatic activity of AChE, aiming to find lead compounds for further optimization leading to drugs with increased efficacy and/or decreased side effects. 124 inhibitors were discovered, with considerable chemical diversity regarding size, polarity, flexibility and charge distribution. An extensive structure determination campaign resulted in a set of crystal structures of protein-ligand complexes. Overall, the ligands have substantial interactions with the peripheral anionic site of AChE, and the majority form additional interactions with the catalytic site (CAS). Reproduction of the bioactive conformation of six of the ligands using molecular docking simulations required modification of the default parameter settings of the docking software. The results show that docking-assisted structure-based design of AChE inhibitors is challenging and requires crystallographic support to obtain reliable results, at least with currently available software. The complex formed between C5685 and Mus musculus AChE (C5685•mAChE) is a representative structure for the general binding mode of the determined structures. The CAS binding part of C5685 could not be structurally determined due to a disordered electron density map and the developed docking protocol was used to predict the binding modes of this part of the molecule. We believe that chemical modifications of our discovered inhibitors, biochemical and biophysical characterization, crystallography and computational chemistry provide a route to novel AChE inhibitors and reactivators
A narrative review of survival normalization in non-Hodgkin lymphoma:useful for better patient counselling and an endpoint for clinical trials?
Bigger is not better: cortisol-induced cardiac growth and dysfunction in salmonids
acceptedVersio
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